Technical Abstract:
Body mass derived from an obesity condition may have detrimental effects on bone health. The purpose of the study was to examine changes in bone structure and serum cytokines related to bone metabolism in obese mice induced by high-fat diet. Male C57BL/6 mice (aged 6 wk) were randomly assigned to one of two groups: control (10 kcal% energy as fat) and high-fat diet (HFD, 45 kcal% energy as fat). Mice were fed the experimental diets for 14 weeks. Serum concentrations of osteocalcin (OC), tartrate-resistant acid phosphatase (TRAP), soluble receptor activator of NF-'B ligand (sRANKL), osteoprotegerin (OPG), and leptin were measured. Bone marrow cells were cultured and stained for osteoclast formation. Trabecular and cortical bone structure of the proximal femur were evaluated by micro-computed tomography. Mice fed the HFD had lower OC but higher TRAP, OPG, and leptin concentrations than those fed the control diet. There were more multinucleated TRAP positive osteoclasts in HFD fed mice than in control diet fed mice. There were no significant differences in serum RANKL concentrations between the two groups. Despite being much heavier, mice fed the HFD had lower bone volume, bone volume/total volume, trabecular thickness, and connectivity density compared to control mice. In addition, trabecular separation was higher in HFD fed mice than control diet fed mice. Our data suggest that HFD diet affects the process of bone formation and resorption and obesity induced by a HFD is detrimental to trabecular bone in the femur in mice.